The advent of the "information age" and the accompanying proliferation of computerized devices for generating and using digitized information has resulted a number of different machines and methods for the sharing of such information between users of such devices. This digitized information takes many different forms, including but not limited to digitized voice and other sound, digitized pictures (both moving and still) and data in many different formats. Given the great variety of types of digital data being generated, it is not surprising that quite a few methods for sharing such data have been devised, it being quite natural that different types of data might optimally be transmitted by different means. The most obvious, although certainly not the only, differences between the transmission requirements of disparate data types are the relative complexity of the data and the rapidity with which a quantity of data must be transmitted. Simple data transmission may be accomplished at relatively low rates while, at the other end of the spectrum, digital moving pictures require a wide bandwidth and high transmission frequency to update an image sufficiently quickly (even with the use of sophisticated data compression techniques).
In fulfillment of these various needs, local area network systems ("LANs") of various types have been developed for communication over short distances, and a further variety of wide area network systems ("WANs"), such as ARPANET, INTERNET, and USENET, have been developed for communication over longer distances. Fiber optic transmission systems, such as the Fiber Distributed Data Interface ("FDDI") and Distributed Queue Dual Bus ("DQDB") have been developed more recently. Even networks that operate at gigabit (billion bits per second) speeds and which consist of parallel connections between computers, such as a network marketed by Ultra Network Technologies, are available for linking supercomputers. At the present time, special networks have also been implemented for different services such as voice, data and video. While some of these networks have been adaptable to more than one data format, each has been restricted to only a limited spectrum of data types and the various networks in common usage are generally mutually incompatible.
While many single purpose data transmission means and methods were well adapted for their intended purpose, it became evident some time ago that it would be desirable to transmit more than one type of data by the same means. One of the first instances of this occurred in LAN type settings wherein it was found to be desirable to be able to transmit both voice and data over the same switched communications lines. In response to the need to communicate a variety of types of digital information, Integrated Services Digital Networks ("ISDN") have been developed for communicating integrated voice and data messages. However, early versions of ISDN methods have been limited in bandwidth such that moving pictures and other such time compacted information are not amendable to transmission thereby. A standard for a Broadband Integrated Services Digital Network ("BISDN") which will have the necessary transmission capabilities is being considered, and the International Telegraph and Telephone Consultive Committee ("CCITT") has published a Study Group XVIII Report R 34 with recommendations concerning BISDN. Asynchronous Transfer Mode ("ATM") is the transfer mode for implementing BISDN, and ATM is independent of the physical means of transport of BISDN signaling. The essence of BISDN is versatility, and so the proposals for its implementation leave it up to independent inventors to devise means for implementing communications in accordance with the proposed functional criteria. According to paragraph 2.3 of the above mentioned CCITT report, "The BISDN architecture is detailed in functional terms and is, therefore, technology and implementation independent".
Clearly, it would be advantageous to create a "technology and implementation" which would implement digital communications according to the BISDN defined functions. In some small degree, such means are indirectly assumed by the defined application. By specific intent, the detailed nature of such means is not defined by the functions themselves. Indeed, it is contemplated that a variety of such means may be developed to accomplish various aspects of the defined functions. While it may be relatively easy to implement specific functions of BISDN, prior to the present invention a means for more general implementation of these functions has not been defined. Furthermore, while it might be a more straightforward (although still quite complicated) engineering task to bring about universal implementation of BISDN functions through the use of very expensive high speed computers which could provide the necessary processing power to handle several broad bandwidth signals in parallel, prior to the present invention there has been no general means of implementation of BISDN which could be accomplished using commonly available and relatively inexpensive small computing devices such as personal computers and the like.
To the inventors' knowledge, no means for implementing the range of BISDN functional capabilities has been developed. All concepts for such means which have been advanced have been either limited in functional capability or else have been too expensive to implement for broad based consumer level acceptance.